The importance of agriculture to the economy cannot be overstated. To foster strong agricultural production, a myriad of treatments for agricultural substrates exist. Such treatments are diverse and include pesticides, growth promoters, fertilizers, and the like. Increasing the effectiveness of these treatments is desirable as agricultural production is facilitated.
There are several factors commonly used to evaluate the effectiveness of topical agricultural or horticultural treatments.
One factor is the retention of the treatment on the plant surface for a time sufficient to achieve the desired result. In this connection, adequate retention times indicate that properties such as resistance to time, wind, water, mechanical or chemical action are possessed.
Another factor is proper coverage of the treatment to provide appropriate coverage over the plant surface. Proper coverage may involve modifying the surface tension of spray droplets, increasing surface wetting, and/or enhancing coverage.
Another factor is the nature of the deposition itself, which needs to be appropriate to maximize the effect of the application.
It is difficult to provide topical agricultural or horticultural treatments with desirable retention characteristics, desired deposition, and proper coverage. For example, often, improving retention characteristics results in reducing proper coverage, and vice versa. In another example, improving coverage can have undesirable deposition characteristics. A key strategy in applying to plants is the consideration of the hydrophobic to hydrophilic nature of plant surfaces. Also, substrate characteristics such as orientation, form, purity, texture, and rigidity are to be considered.
Agricultural treatment substrates are both hydrophobic and hydrophilic surfaces and these two groups are defined by the contact angle of a sessile droplet resting on the target surface. Target surfaces are considered hydrophilic when the contact angle of a water droplet is less than 90° and considered hydrophobic when the contact angle is greater than 90°.
The problems associated with the application of liquids to hydrophobic and hydrophilic surfaces are well known.
Applications of liquids to hydrophobic surfaces are problematic as these surfaces repel aqueous-based sprays. This is usually remedied by use of a surfactant. However, depositions with surfactants used by themselves can be too thin and can run off hydrophobic surfaces and, in addition, can be extremely thin and have extreme run off of co-targeted hydrophilic surfaces. Thus, in terms of hydrophilic surfaces, conventional agricultural surfactants (spreaders) used by themselves can overspread and cause extreme runoff resulting in poor coverage.
The application of liquids to hydrophilic surfaces poses fewer problems because these surfaces readily wet. The main problem encountered with applying liquids to hydrophilic surfaces is the phenomenon known as over-wetting that results in overspreading and can cause approximately two-thirds of the spray material to run off the surface and be wasted. Reducing spray volumes will generally reduce, but not eliminate, this problem.
These problems are also seen specifically in the delivery of agricultural particle films. There are two techniques currently used to improve delivery of particles to target surfaces. One is the retention of the treatment on the plant surface by the use of stickers. The second factor is the use of spreaders to improve coverage of the treatment. These arts can enhance spray retention on hydrophobic surfaces but overspreading and droplet retraction occurs which leads to the problem of thin, spotty deposits and/or non-uniform film formation. When spreaders are used in hydrophilic surfaces run off is a problem.
There is also a need for spreading and sticking agents that have relatively equal deposition properties on both hydrophobic and hydrophilic surfaces. This is particularly needed in plants that have both hydrophobic and hydrophilic surfaces such as tomatoes and grapes wherein generally the fruit is hydrophobic and the foliage is hydrophilic. In such a case, a given level of conventional spreaders may be ideal for the hydrophobic part of the plant, but may induce overspreading on the hydrophilic part of the plant.
SURROUND® WP crop protectant is labeled as 95% kaolin and 5% other ingredients. The specimen label discloses that initial application over waxy surfaces such as mango fruit may not spread and instructs the user to see Engelhard supplemental labeling for further information on use of spreaders. Commonly assigned U.S. Pat. No. 6,514,512 teaches that SURROUND® WP crop protectant is calcined kaolin with an organic spreader/sticker. However, in commercial usage and as seen in FIG. 9, SURROUND® WP crop protectant does not have film-forming spreading (defined below) on hydrophobic surfaces but adequate depositions do occur on hydrophilic surfaces.
Particle films are used for sunburn and heat stress reduction and rely on the light properties passing through the particle film, in particular the controlled blockage of visible, UV, and IR light, to gain beneficial effects. Improved particle film treatments with improved controlled blockage of light and film-forming spreading (defined below) for both hydrophilic and hydrophobic agricultural substrates are therefore desired.